Pseudoxanthoma Elasticum (PXE) is a hereditary disease characterized by ectopic calcification of elastic fibers in the dermis, the eye and the vasculature. We have demonstrated the presence of a proteolytic enzyme from PXE fibroblasts that can degrade proteoglycans. The objectives of the proposed research are to develop a sensitive and rapid assay for this proteolytic enzyme, to purify the protease and to develop an antibody to the purified enzyme. In addition, the role of the proteolytic enzyme in the pathogenesis and calcification of elastic tissue will be studied by growing smooth muscle cells in tissue culture; these cells will lay down an extracellular matrix of elastin and collagen. PXE or normal fibroblasts will be subcultured over the connective tissue matrix and used to study the condition that may facilitate the development of the lesions within the elastic fiber that are characteristically seen in affected PXE dermis. The role of gamma-carboxyglutamic acid (Gla) in ectopic calcification and in the mineralization of bone has been described. Preliminary evidence from this laboratory suggests that Gla may be present within the affected PXE dermis. This observation will be confirmed and extended to determine whether PXE fibroblasts synthesize a substance that contains Gla. Furthermore, the protease will be evaluated for its content of Gla, since it seems possible that a protein synthesized in association with abnormal calcification may be a calcium-dependent protein.